Surgery on the human eye has become commonplace in recent years. Many patients pursue eye surgery as an elective procedure in order to avoid the use of contacts or glasses, while other patients find it necessary to pursue surgery to correct an adverse condition in the eye. Such adverse conditions may include, for example, cataracts. A cataract increases the opacity of the natural lens of the eye, causing impaired vision or blindness. Correction may be achieved by surgically removing a cloudy or diseased lens in the patient's eye and replacing it with an artificial lens, known as an intraocular lens (IOL).
The anatomy and physiology of the human eye is well understood. Generally speaking, the structure of the human eye includes an outer layer formed of two parts, namely the cornea and the sclera. The middle layer of the eye includes the iris, the choroid, and the ciliary body. The inner layer of the eye includes the retina. The eye also includes, physically associated with the middle layer, a crystalline lens that is contained within an elastic capsule, referred to herein as the lens capsule, or capsular bag.
Image formation in the eye occurs by entry of image-forming light to the eye through the cornea, and refraction by the cornea and the crystalline lens to focus the image-forming light on the retina. The retina provides the light sensitive tissue of the eye.
Functionally, the cornea has a greater, and generally constant, optical power in comparison to the crystalline lens. The power of the crystalline lens, while smaller than that of the cornea, may be changed when the eye needs to focus at different distances. This change, or “accommodation,” is achieved by changing the shape of the crystalline lens. Accommodation, as used herein, includes the making of a change in the focus of the eye for different distances. For example, in order to change the shape of the crystalline lens for accommodation, the ciliary muscles may relax to cause ligaments (zonules) that support the crystalline lens to relax, thereby allowing the crystalline lens to become more rounded.
The iris operates to change the aperture size of the eye. More specifically, the diameter of the incoming light beam is controlled by the iris, which forms the aperture stop of the eye, and the ciliary muscles may contract, as referenced above, to provide accommodation in conjunction with any needed change in the size of the aperture provided by the iris. The opening, or aperture, in the iris is called the pupil.
Correction of defects or degradation in the aspects of the eye may occur surgically, as mentioned above, or non-surgically. In a simple example, it is common to wear glasses or contact lenses to improve vision by correcting myopic (near-sighted), hyperopic (far-sighted) and astigmatic eyesight. Rather than relying on glasses or contacts, elective laser refractive surgery, or other eye surgery, may serve to improve the refractive state of the eye, and may thereby decrease or eliminate dependence on glasses or contact lenses. Additional surgeries may include various methods of surgical remodeling of the cornea, or cataract surgery, for example.
Presbyopia, referenced above, is an adverse condition in which the eye loses the ability to accommodate. Presbyopia is one of the adverse conditions of the eye for which the aforementioned surgical and non-surgical treatments have proven relatively successful. However, many of the aforementioned treatments, such as those in which eye-glasses and contact lenses are employed, provide only temporary solutions for adverse eye conditions and particularly for adverse eye conditions such as presbyopia that cause a loss of capability for accommodation.
In other, non-ocular medical fields, in order to provide a more long-lasting solution for biologic adversities, externally controllable treatments, such as ionic polymer-metal composites, have recently been explored as possible treatment options. For example, these composites have been explored for use with artificial limbs and/or limbs that lack sufficient muscular and/or nervous system control or strength.
Accordingly, it may be advantageous to employ the use of externally controllable treatments, such as ionic polymer-metal composites, to the eye, and, in particular, to the cornea. Such a solution may provide another, potentially more viable and long term solution to the correction of adverse eye conditions, such as presbyopia, by allowing for alteration of a shape of the cornea.